Additional info on audio/video derivatives

• h.264 / mp4 derivatives:

            video (h.264):
            640x480 (width scaled if wider/narrower than 4x3 ratio)
            ~768kb/sec (maxrate)
            audio (AAC):
            stereo, 128kb/sec 44.1Khz sampling
            

• ogv derivatives:

            video (theora):
            400x300 (width scaled if wider/narrower than 4x3 ratio)
            target ~512 kb/sec
            audio (vorbis):
            stereo, ~128kb/sec 44.1Khz sampling
            

• mp3 derivatives:

              MP3 format, stereo, lame compressor "-standard" parameter/setting
              which targets ~140 kb/sec
            

Advanced techniques and help

To remove and/or prevent a particular derivative format

If for some reason, you prefer to not have your item create the derivative of one or more formats, you can upload to your item a special "rules" named "_rules.conf". That file should be a text file, with a single line of each format to disallow.

So, for example, to make (all videos in) a video item *not* create our "Animated GIF" and "h.264" formats, you would upload "_rules.conf" containing the following:
Animated GIF h.264

To prohibit *just* video and audio derived formats that are "lossy" (eg: mp3, ogg, mp4, ogv) you would upload "_rules.conf" containing the following:
CAT.lossy

To prohibit *all* derived formats, you would upload "_rules.conf" containing the following:
CAT.ALL

To make any previously created derivatives "disappear" after adding or updating a "_rules.conf" file to an item, use the "Item Manager" link to submit a "derive" task (which will remove the undesired derivatives). (Find the "Edit Item" link in the upper right of your item while you are logged in, click "change the information" link, click the "Item Manager" link near the top of that page, then hit the "derive" button).